The invention relates to a method of recognizing objects, in particular detecting defects on workpieces, preferably on shot cores or core packets, wherein the object is illuminated by a light source and recorded or detected by means of a camera, and wherein the data obtained from the recording are processed and, if need be, stored by means of a computer.
Furthermore, the invention relates to an apparatus for recognizing objects, in particular for applying the method according to the invention.
In generic terms, the invention quite generally relates to a method for recognizing objects or detecting defects on workpieces. Quite particularly, this method is suited for detecting defects on shot cores or core packets. To this extent, the invention also relates, among other things, to the field of foundry practice.
For casting mold parts of any kind, foundry cores or molds are made in most cases in separate pieces, combined, and joined to a casting mold or a core packet. These core packets are then filled with a molten metal for making, for example, a metallic work piece. In the series production, the core packets to be filled with the molten metal pass, one after the other, through a production line.
In this connection, it is particularly important that the workpieces cast in the core packets require an extremely long cooling phase, which often extends over several hours. Only after this cooling phase, is it possible to inspect the cast workpiece or part. Consequently, it is possible to find out only several hours after the casting, and thus likewise only several hours after the core shooting, whether the part cast in the core packet is indeed free of defects.
Should a defective core have been used, it would be possible to detect resultant rejects only hours after making the core. Should it in turn be a systematic, for example, a recurrent defect on the core because of a defect on the tool, rejects would be produced for hours before the defect is identified on the cast part. As previously mentioned, the defective cores responsible for these rejects could originate not only from defects in the tool of the core shooting machine, but also from direct damage to the cores during their handling, transportation, or assembly. In any event, it is not justifiable to be able to detect defects and thus rejects only after completing the casting operation, or during the inspection of the cast parts that have already cooled.
Moreover, damage to mold parts and/or tools may occur not only in the immediate vicinity of the shooting device, but rather also in any handling of the mold part and/or tool, during transportation, in the machining of the mold parts, during the cleaning of the tools, and in particular also during the assembly of the mold parts to whatever shape of a mold packet.
Core and shell shooting machines of the above-described kind have been known from practice for many decades. For example, one may refer to DE 31 48 461 C1, which discloses a core and shell shooting machine as made by Applicant.
Likewise, DE 44 34 798 A1 discloses a core and shell shooting machine, which is provided with at least one visual inspection of the tool. Last but not least, the visual control as addressed in DE 44 34 798 A1 is not practicable, inasmuch as it is not possible to observe the tool constantly within the scope of a fully automatic production. For a visual inspection, a skilled worker would have to observe the tool constantly, i.e., after each shooting operation. Even if one performed such a visual observation or inspection, the fate of an ejected core that is to be transported, machined, or assembled to a packet, would be left fully open, inasmuch as defects or damage may also occur during the handling or machining of the cores, during the transfer of the cores, or even during the assembly of the cores to packets.
DE 195 34 984 C1 already discloses a generic method, wherein the mold part or the core is measured, among other things, by a noncontacting technique even after its removal from the core shooting machine. This occurs in an advantageous manner by means of a camera, which requires in this instance an adequate illumination. Concealed regions or undercuts can be inspected by this kind of method only, when either a plurality of cameras are used for the image recording, and thus likewise for detecting defects, or when a camera is moved relative to the location of the object or core being examined. Both variants require a considerable expenditure for apparatus, and therefore are problematic for cost reasons alone. Furthermore, the arrangement of a plurality of cameras interferes with the direct surroundings of the particular core, and thus with the manipulators being used in this region.
It is therefore an object of the present invention to improve and further develop a method of the generic kind as well as a corresponding apparatus for object recognition, in particular for detecting defects on workpieces, preferably on shot cores or core packets in such a manner that they enable an adequately satisfactory object recognition and defect detection with the least possible expenditure for apparatus or construction.